@Mike9241 Thank you for the response. I guess I should have said "current year tax", which is what Form 2210 Line 4 calls it. It's also the same amount as Form 1040 Line 24, which is called "total tax".
Anyway, Form 2210 Line 5 multiplies that by 90%, which is what Line 6 (withholding taxes) is subtracted from. The difference is less than $1000, which is too low for a penalty according to Line 7. However, TT says the penalty is $2. So, which is correct, TT or Form 2210.
